Studies of religious and other cultural groups tend to be particularistic or focus on one or more axes of variation. In this article we develop a more comprehensive approach to studying cultural diversity that emulates the study of biological diversity. We compare our cultural ecosystem approach with the axis approach, using the distinction between "tight" and "loose" cultures as an example. We show that while the axis approach is useful, the cultural ecosystem approach adds considerable value to the axis approach. We end by advocating the establishment of field sites for the study of religious and cultural diversity, comparable to biological field sites.
ARTICLE HISTORYReligions and other cultural forms exist in almost endless variety, with old forms disappearing and new forms arising all the time. It is easy to use the word "evolution" to describe these changes, but past efforts to develop a comprehensive theory of cultural evolution did not become widely accepted and in retrospect can be seen to suffer from misconceptions that do not follow from evolutionary theory (such as cultural evolution as a linear progression from "savagery" to "civilization"; see Carniero, 2003 for a review). More recent research on human cultural evolution promises to succeed where past efforts have failed and enable a more rigorous comparison between religious diversity, cultural diversity, and biological diversity. A useful overview based on a recent conference is provided by Richerson and Christiensen (2013) in addition to other references cited below.Studies of religious and cultural diversity that are not based on evolution tend to be particularistic, reflecting detailed scholarship on single systems but lacking a common methodology or broader theoretical framework. When attempts at integration are made, they often take the form of identifying axes of variation, such as between strict vs. lax churches (Iannacconeeven gradients in the incidence of diseases and parasites (Fincher & Thornhill, 2012). Statistical methods such as factor analysis are sometimes employed to identify multiple axes of variation (Hofstede, 1980). These attempts at integration are more synthetic than particularistic approaches but the choice of axes (other than by factor analysis) tends to be haphazard, isolated literatures grow around the study of each axis, and different axes are seldom systematically related to each other.In this article, we will first summarize the current status of cultural evolutionary theory and evolutionary religious studies, both of which have become centered on group-level functional organization. Second, we will outline the cultural ecosystem approach to the study of religious and cultural diversity, modeled on the study of biological diversity. Third, we will discuss the axis-of-variation approach (hereafter called the axis approach), focusing on the distinction between "tight" and "loose" cultures as an extended example. We have chosen the tight/loose axis as an exemplar because it has been used mostly to study variation in trad...